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Merge pull request #4268 from JackStouffer/issue15973

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[Issue 15973]: nextPow2 and truncPow2 rely on processor specific …
This commit is contained in:
Rainer Schuetze 2016-05-02 18:26:14 +02:00
commit aa8cf8646f
1 changed files with 27 additions and 26 deletions
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51
std/math.d
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@ -7333,28 +7333,17 @@ private T powIntegralImpl(PowType type, T)(T val)
{ {
import core.bitop : bsr; import core.bitop : bsr;
Unqual!T x = val; if (val == 0 || (type == PowType.ceil && (val > T.max / 2 || val == T.min)))
return 0;
static if (isSigned!T)
if (x < 0)
x = abs(x);
if (x == 0)
return x;
static if (type == PowType.ceil)
x = cast(Unqual!T) (Unqual!T(1) << bsr(x) + 1);
else else
x = cast(Unqual!T) (Unqual!T(1) << bsr(x)); {
static if (isSigned!T) static if (isSigned!T)
if (val < 0) return cast(Unqual!T) (val < 0 ? -(T(1) << bsr(-val) + type) : T(1) << bsr(val) + type);
return -x; else
return cast(Unqual!T) (T(1) << bsr(val) + type);
return x; }
} }
pragma(inline, true)
private T powFloatingPointImpl(PowType type, T)(T x) private T powFloatingPointImpl(PowType type, T)(T x)
{ {
if (!x.isFinite) if (!x.isFinite)
@ -7380,9 +7369,12 @@ private T powFloatingPointImpl(PowType type, T)(T x)
} }
/** /**
* Gives the next power of two after $(D val). $(T) can be any built-in * Gives the next power of two after $(D val). `T` can be any built-in
* numerical type. * numerical type.
* *
* If the operation would lead to an over/underflow, this function will
* return `0`.
*
* Params: * Params:
* val = any number * val = any number
* *
@ -7410,15 +7402,15 @@ T nextPow2(T)(const T val) if (isFloatingPoint!T)
assert(nextPow2(-2) == -4); assert(nextPow2(-2) == -4);
assert(nextPow2(-10) == -16); assert(nextPow2(-10) == -16);
assert(nextPow2(uint.max) == 1); assert(nextPow2(uint.max) == 0);
assert(nextPow2(uint.min) == 0); assert(nextPow2(uint.min) == 0);
assert(nextPow2(size_t.max) == 1); assert(nextPow2(size_t.max) == 0);
assert(nextPow2(size_t.min) == 0); assert(nextPow2(size_t.min) == 0);
assert(nextPow2(int.max) == int.min); assert(nextPow2(int.max) == 0);
assert(nextPow2(int.min) == -1); assert(nextPow2(int.min) == 0);
assert(nextPow2(long.max) == long.min); assert(nextPow2(long.max) == 0);
assert(nextPow2(long.min) == -1); assert(nextPow2(long.min) == 0);
} }
/// ///
@ -7493,6 +7485,15 @@ T nextPow2(T)(const T val) if (isFloatingPoint!T)
} }
} }
@safe @nogc pure nothrow unittest // Issue 15973
{
assert(nextPow2(uint.max / 2) == uint.max / 2 + 1);
assert(nextPow2(uint.max / 2 + 2) == 0);
assert(nextPow2(int.max / 2) == int.max / 2 + 1);
assert(nextPow2(int.max / 2 + 2) == 0);
assert(nextPow2(int.min + 1) == int.min);
}
/** /**
* Gives the last power of two before $(D val). $(T) can be any built-in * Gives the last power of two before $(D val). $(T) can be any built-in
* numerical type. * numerical type.